It's a bit of a weird question, but i wonder if others have any insights:
i've noticed that the "chain animal" job needed to tie up my goblin prisoners is only ever taken by very few dwarfs. If none of those are available/willing, the jobs can stay dormant for weeks, no matter how many idlers are present. In addition, only one chaining job will exist at a time. If ten goblins are assigned to chains, they'll still be moved one at a time (i.e. there's always at most one goblin in transit and the next job doesn't get lined up before the previous finishes).
The only common thing i've seen among the goblin handlers is that they all have the "animal training" labour active, and in fact seem to include _all_ animal trainers (i have only four in total), as demonstrated by looking at the "train animal" option in the z-animal screen, which only gives active trainers for "assign training by individual dwarf". Have others observed this as well, or is there some other skill/labour around that's a better fit? If no-one has animal training active, who chains the goblins? - or will they remain unchained?
Something similar seems to be going on with "cage large creature" jobs, but i haven't watched those in detail - i'm more attentive of goblin chaining, because i'm afraid one might get loose, so observe those jobs closely. The "one job at a time" rule does apply to caging jobs, but i don't know how picky they are concerning dwarfs.
Bring to pasture/throw into a pit work differently, those are proven non-labour jobs and multiple can be active simultaneously.